High-field Magnetic Resonance Research Articles

Spontaneous regression of extradural intraspinal cysts in a dog: a case report

BackgroundExtradural intraspinal cysts are fluid accumulations that appear to be associated with increased motion at vertebral joints.Case presentationWe report the spontaneous regression of lumbar and lumbosacral cysts (presumably synovial cysts) and the unusual occurrence of an S1–2 extradural intraspinal cyst in a dog. The dog presented with lumbosacral pain. Six extradural intraspinal cysts were observed on high-field magnetic resonance imaging from L5–6 to S1-S2. The cysts between L5–6 and L7-S1 ranged from 0.12 to 0.44cm2 at their largest area. The largest cyst was located at S1–2 (left), measuring 0.84 cm2 at its largest view. The dog was medically managed. A follow-up magnetic resonance imaging scan was obtained 3.5 years after the first imaging. All cysts except the one at S1–2 had reduced in size. Mean reduction in size was 59.6% (35–81%).ConclusionsIn summary, we report a case with multiple extradural intraspinal cysts that underwent spontaneous regression of all but one cyst during a 3.5-year follow-up period. Whether this is a single occurrence, or is part of the natural history of these cysts in the lumbosacral region of dogs, remains to be established. Spontaneous regression of intraspinal cysts had not been described in dogs.

Tissue-specific changes in size and shape of the ligaments and tendons of the porcine knee during post-natal growth.

Prior studies have analyzed growth of musculoskeletal tissues between species or across body segments; however, little research has assessed the differences in similar tissues within a single joint. Here we studied changes in the length and cross-sectional area of four ligaments and tendons, (anterior cruciate ligament, patellar tendon, medial collateral ligament, lateral collateral ligament) in the tibiofemoral joint of female Yorkshire pigs through high-field magnetic resonance imaging throughout growth. Tissue lengths increased by 4- to 5-fold from birth to late adolescence across the tissues while tissue cross-sectional area increased by 10-20-fold. The anterior cruciate ligament and lateral collateral ligament showed allometric growth favoring change in length over change in cross-sectional area while the patellar tendon and medial collateral ligament grow in an isometric manner. Additionally, changes in the length and cross-sectional area of the anterior cruciate ligament did not increase as much as in the other ligaments and tendon of interest. Overall, these findings suggest that musculoskeletal soft tissue morphometry can vary within tissues of similar structure and within a single joint during post-natal growth.

Does Injection of Hyaluronic Acid Protect Against Early Cartilage Injury Seen After Marathon Running? A Randomized Controlled Trial Utilizing High-Field Magnetic Resonance Imaging

Background: Previous studies have shown that runners demonstrate elevated T2 and T1ρ values on magnetic resonance imaging (MRI) after running a marathon, with the greatest changes in the patellofemoral and medial compartment, which can persist after 3 months of reduced activity. Additionally, marathon running has been shown to increase serum inflammatory markers. Hyaluronic acid (HA) purportedly improves viscoelasticity of synovial fluid, serving as a lubricant while also having chondroprotective and anti-inflammatory effects. Purpose/Hypothesis: The purpose was to investigate whether intra-articular HA injection can protect articular cartilage from injury attributed to marathon running. The hypothesis was that the addition of intra-articular HA 1 week before running a marathon would reduce the magnitude of early cartilage breakdown measured by MRI. Study Design: Randomized controlled trial; Level of evidence, 2. Methods: After institutional review board approval, 20 runners were randomized into receiving an intra-articular injection of HA or normal saline (NS) 1 week before running a marathon. Exclusionary criteria included any prior knee injury or surgery and having run >3 prior marathons. Baseline 3-T knee MRI was obtained within 48 hours before the marathon (approximately 5 days after injection). Follow-up 3-T MRI scans of the same knee were obtained 48 to 72 hours and 3 months after the marathon. The T2 and T1ρ relaxation times of articular cartilage were measured in 8 locations—the medial and lateral compartments (including 2 areas of each femoral condyle) and the patellofemoral joint. The statistical analysis compared changes in T2 and T1ρ relaxation times (ms) from baseline to immediate and 3-month postmarathon scans between the HA and NS groups with repeated measures analysis of variance. Results: Fifteen runners completed the study: 6 women and 2 men in the HA group (mean age, 31 years; range, 23-50 years) and 6 women and 1 man in the NS group (mean age, 27 years; range, 20-49 years). There were no gross morphologic MRI changes after running the marathon. Postmarathon studies revealed no statistically significant changes between the HA and NS groups in all articular cartilage areas of the knee on both T2 and T1ρ relaxation times. Conclusion: Increased T2 and T1ρ relaxation times have been observed in marathon runners, suggesting early cartilage injury. The addition of intra-articular HA did not significantly affect relaxation times in all areas of the knee when compared with an NS control.

Denoising High-Field Multi-Dimensional MRI With Local Complex PCA.

Modern high field and ultra high field magnetic resonance imaging (MRI) experiments routinely collect multi-dimensional data with high spatial resolution, whether multi-parametric structural, diffusion or functional MRI. While diffusion and functional imaging have benefited from recent advances in multi-dimensional signal analysis and denoising, structural MRI has remained untouched. In this work, we propose a denoising technique for multi-parametric quantitative MRI, combining a highly popular denoising method from diffusion imaging, over-complete local PCA, with a reconstruction of the complex-valued MR signal in order to define stable estimates of the noise in the decomposition. With this approach, we show signal to noise ratio (SNR) improvements in high resolution MRI without compromising the spatial accuracy or generating spurious perceptual boundaries.

Mesial temporal lobe epilepsy: Revisiting the relation of hippocampal volumetry with memory deficits

ObjectiveNeuropsychological tests can infer the lateralization of the epileptogenic focus, associating verbal memory to mesial structures in the left temporal lobe and visual or nonverbal memory to the right side. High-field magnetic resonance imaging (MRI) with high-resolution protocols allows acquisitions suitable for advanced postprocessing with precise volumetry of brain structures, and functional MRI demonstrates evidence that epilepsy should be seen as a network pathology, involving several structures in the brain. Since the literature showing associations between the volumetry of brain structures in left and right mesial temporal lobe epilepsy (MTLE) and verbal and visual memory performance on neuropsychological tests is conflicting, we revisited these relationships, considering the hippocampal volumetry of patients with unilateral MTLE. MethodsAutomatized hippocampal volumes were obtained using FreeSurfer software from MRI exams of 35 patients with unilateral MTLE and hippocampal atrophy and homolateral ictal onset zone defined by video electroencephalography concordant to the side of hippocampal volume reduction (15 on the left side). Verbal memory was assessed using the Rey Auditory-Verbal Learning Test (RAVLT), and visual memory tests employed the Rey–Osterrieth Complex Figure Test (ROCFT). The statistical analysis explored relationships between hippocampal volumetry, lateralization, and performance on memory tests. ResultsIn general, we observed deficits in both verbal and visual memory for patients with left and right hippocampal volume reduction. Patients with left hippocampal volume reduction had poorer performance on verbal memory tests compared with those with right hippocampal atrophy (t = −3.813, p < 0.001). Visual memory deficits were seen on both left and right MTLE without a statistically significant difference (t = 0.074, p = 0.942). The correlation between the Hippocampal Asymmetry Index (HAI) and visual and verbal Z-scores was significant only for visual Z-score in right MTLE (R = −0.45, p = 0.048). ConclusionsVerbal memory deficit seems to be more consistent in patients with left hippocampal volume reduction. Although it had only a moderate correlation to HAI, visual memory deficit is suggested as a poorer indicator for right MTLE. Considering that verbal and visual memory deficits are seen on both right and left MTLE, MTLE should not be regarded as a unilateral, focal, or local insult but as a multifactorial and network pathology, possibly involving several brain structures.

P11.42 Magnetic targeting of the granzyme B functionalized nanoparticles for therapy of glioblastoma

Abstract BACKGROUND Magnetic drug targeting by employing external magnetic fields represents a promising approach for treatment of glioblastoma. To increase the anti-tumor therapeutic effect magnetic nanocarriers could be functionalized with tumor-targeting bioligands such as granzyme B (GrB). The serine protease GrB that is produced as an effector molecule by activated NK and T cells can induce specific tumor cell apoptosis. MATERIAL AND METHODS The targeting potential of the dextran-coated superparamagnetic iron oxide nanoparticles conjugated with GrB (GrB-SPIONs) was assessed in glioblastoma cells (U87, C6, GL261) by flow cytometry, confocal and electron microscopies. Magnetic field strength (320 mT) in the models of U87 glioblastoma in NMRI nu/nu mice and C6 glioma in Wistar rats was achieved by employing NdFeB cylindrical ferromagnet. The irradiation of the implanted tumors was performed using the CT-image guided Small Animal Radiation Research Platform (SARRP). Accumulation of the nanoparticles was assessed in paraffine-embedded specimens employing Prussian blues staining. Sections were additionally analyzed by IHC for apoptosis (caspase 3). RESULTS Synthesized GrB-SPIONs incorporated into the cytoplasm of tumor cells via the endolysosomal pathway and induced apoptosis in a dose-dependent manner. Intravenous injection of GrB-SPIONs resulted in the glioma-specific retention of the nanoparticles as was shown by high-field (11 T) magnetic resonance imaging and biodistribution studies (NLR-M2 measurements). Magnetic targeting of the nanoparticles in vivo drastically enhanced the accumulation of nanoparticles to the location of the magnet. Thus the local retention of nanoparticles was 12.3-fold higher as compared to application of GrB-SPIONs without external magnetic field. The presence of granzyme B on SPIONs has been shown to promote tumor cells death (IHC staining for caspase 3) and significantly increased overall survival. A combination of nanoparticle treatment with a single radiation dose (10 Gy) significantly prolonged the survival of rats as compared to animals treated only with magnetic targeting of GrB-SPIONs or radiotherapy alone (P&lt;0.001). CONCLUSION Single-agent therapy with GrB-SPIONs demonstrated an impressive increase in overall survival of tumor-bearing animals. Combinatorial regimen employing magnetic targeting and stereotactic radiotherapy further enhanced the therapeutic potential of magnetic conjugates.

Designing and building a low-cost portable FT-NMR spectrometer in 2019: A modern challenge

Abstract High-field Fourier-Transform Nuclear Magnetic Resonance (FT-NMR) spectroscopy is a high performance spectroscopic technique that is essential in many analytical fields. The non-destructive nature of NMR makes it a preferred means of analyzing chemical and biological environments. Compact benchtop NMR spectrometers are low-cost alternatives to conventional high-field and high-resolution spectrometers. A research laboratory may want to develop its own compact FT-NMR spectrometer (home-built benchtop NMR) with a very low financial cost (∼10 k€). But why? First of all, to use it punctually as an additional channel (nucleus X) to a high-resolution spectrometer, and also to be able to couple it with complementary physics instruments such as an optical microscope to study spin diffusion in semiconductors, for instance. In addition, a home-built NMR spectrometer can be used with a low-field permanent magnet for the quantification of species that does not necessarily require high-resolution, avoiding the need for weekly and expensive cryogenic services. Outside the research laboratory, this portable NMR can be used for the in situ analysis of outdoor natural environments. Finally, this compact spectrometer is naturally dedicated to the teaching of NMR technique and is open to the study of the basic electronic functions that constitute an NMR spectrometer. The main question then arises: how to build a robust Home-Built” NMR? In this article, we describe the realization of an NMR instrument based on electronic components and boards (LNA, ADC, FPGA, ARM, DDS…) easily commercially available, allowing one to obtain a benchtop NMR instrument presenting both a high acquisition dynamics and a good signal-to-noise ratio.

Accuracy of Automatic Structure Propagation for Daily High-Field Magnetic Resonance Image-Guided Head and Neck Radiotherapy

Accuracy of Automatic Structure Propagation for Daily High-Field Magnetic Resonance Image-Guided Head and Neck Radiotherapy

Tesseral superconducting shim coil design with quasi-saddle geometry for use in high-field magnet system.

Superconducting shim coils are frequently used in high-field magnetic resonance imaging or nuclear magnetic resonance system for their high sensitivity and shimming strength. The design of superconducting shim coils is based on the spherical harmonic decomposition, and each shim coil is normally dedicated for correcting one specific harmonic component. Conventional superconducting shim coil with a saddle loop has observable winding error near the corner, which gives rise to arc transformation when winding layer by layer. Simulation analysis shows that the arc corner transformation will induce the magnetic field deviation by more than double of the theoretical design ±1%, which may be up to ±3% after real winding. An improved shim coil design method with a quasisaddle geometry was proposed to correct the winding error. With the consideration of both the rounded corner of the saddle loop and the arc side, the new design offers the magnetic field deviation within ±1%. In addition to reducing the winding error, the proposed design also facilitates the winding process.

Neurite orientation dispersion and density imaging reveals white matter and hippocampal microstructure changes produced by Interleukin-6 in the TgCRND8 mouse model of amyloidosis

Extracellular β-amyloid (Aβ) plaque deposits and inflammatory immune activation are thought to alter various aspects of tissue microstructure, such as extracellular free water, fractional anisotropy and diffusivity, as well as the density and geometric arrangement of axonal processes. Quantifying these microstructural changes in Alzheimer’s disease and related neurodegenerative dementias could serve to monitor or predict disease course. In the present study we used high-field diffusion magnetic resonance imaging (dMRI) to investigate the effects of Aβ and inflammatory interleukin-6 (IL6), alone or in combination, on in vivo tissue microstructure in the TgCRND8 mouse model of Alzheimer’s-type Aβ deposition. TgCRND8 and non-transgenic (nTg) mice expressing brain-targeted IL6 or enhanced glial fibrillary protein (EGFP controls) were scanned at 8 months of age using a 2-shell, 54-gradient direction dMRI sequence at 11.1 T. Images were processed using the diffusion tensor imaging (DTI) model or the neurite orientation dispersion and density imaging (NODDI) model. DTI and NODDI processing in TgCRND8 mice revealed a microstructure pattern in white matter (WM) and hippocampus consistent with radial and longitudinal diffusivity deficits along with an increase in density and geometric complexity of axonal and dendritic processes. This included reduced FA, mean, axial and radial diffusivity, and increased orientation dispersion (ODI) and intracellular volume fraction (ICVF) measured in WM and hippocampus. IL6 produced a ‘protective-like’ effect on WM FA in TgCRND8 mice, observed as an increased FA that counteracted a reduction in FA observed with endogenous Aβ production and accumulation. In addition, we found that ICVF and ODI had an inverse relationship with the functional connectome clustering coefficient. The relationship between NODDI and graph theory metrics suggests that currently unknown microstructure alterations in WM and hippocampus are associated with diminished functional network organization in the brain.

Lenticulostriate Arteries and Basal Ganglia Changes in Cerebral Autosomal Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy, a High-Field MRI Study.

Background and Purpose: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) mainly affects the cerebral small arteries. We aimed to analyze changes in the lenticulostriate arteries (LSAs) and the basal ganglia in patients with CADASIL using high-field magnetic resonance imaging (7.0-T MRI).Methods: We examined 46 patients with CADASIL and 46 sex- and age-matched healthy individuals using 7.0-T MRI. The number and length of the LSAs, and the proportion of discontinuous LSAs were compared between the two groups. The Mini-Mental State Examination score, the modified Rankin Scale, the Barthel Index, and the MRI lesion load of the basal ganglia were also examined in patients with CADASIL. We analyzed the association between LSA measurements and the basal ganglia lesion load, as well as the association between LSA measurements and clinical phenotypes in this patient group.Results: We observed a decrease in the number of LSA branches (t = −2.591, P = 0.011), and an increase in the proportion of discontinuous LSAs (z = −1.991, P = 0.047) in patients with CADASIL when compared with healthy controls. However, there was no significant difference in the total length of LSAs between CADASIL patients and healthy individuals (t = −0.412, P = 0.682). There was a positive association between the number of LSA branches and the Mini-Mental State Examination scores of CADASIL patients after adjusting for age and educational level (β = 0.438; 95% CI: 0.093, 0.782; P = 0.014). However, there was no association between LSA measurements and the basal ganglia lesion load among CADASIL patients.Conclusions: 7.0-T MRI provides a promising and non-invasive method for the study of small artery damage in CADASIL. The abnormalities of small arteries may be related to some clinical symptoms of CADASIL patients such as cognitive impairment. The lack of association between LSA measurements and the basal ganglia lesion load among the patients suggests that changes in the basal ganglia due to CADASIL are caused by mechanisms other than anatomic narrowing of the vessel lumen.

The Zurich Pituitary Score predicts utility of intraoperative high-field magnetic resonance imaging in transsphenoidal pituitary adenoma surgery.

It is currently unclear if there are subsets of patients undergoing transsphenoidal surgery (TSS) in which intraoperative high-field magnetic resonance imaging (3T-iMRI) is particularly advantageous. We aimed to investigate whether a radiological grading scale predicts the utility of 3T-iMRI in pituitary adenoma (PA) TSS. From a prospective registry, patients who underwent endoscopic TSS for PA using 3T-iMRI were identified. Adenomas were graded using the Zurich Pituitary Score (ZPS). We assessed improvement after 3T-iMRI in terms of gross total resection (GTR), residual volume (RV), and extent of resection (EOR). Among 95 patients, rates of conversion to GTR after 3T-iMRI decreased steadily from 33% for grade I to 0% for grade IV adenomas, with a statistically significant conversion rate only for grade I (p = 0.008) and grade II (p < 0.001). All grade I adenomas were completely resected after 3T-iMRI. Median RV change was statistically significant for grades I to III, but not for grade IV (p = 0.625). EOR improvement ranged from a median change of 0.0% (IQR 0.0-4.5%) for grade I to 4.4% (IQR 0.0-9.0%) for grade IV, with a significant improvement only for grades I to III (p < 0.05). Interestingly, this study shows that clinical utility of 3T-iMRI is highest in the more "simple" adenomas (ZPS grades I-II) than for the more "complex" ones (ZPS grade III-IV). Grade I adenomas are amenable to GTR if 3T-iMRI is implemented. In grade III adenomas, EOR and RV can be improved to clinically relevant levels. Conversely, in grade IV adenomas, 3T-iMRI may be of limited use.

Experiments on the Effects of Local Normal Transitions in Multi-Stacked No-Insulation REBCO Pancake Coils

No-insulation (NI) coils are an important technique for high-field magnetic resonance imaging (MRI). One of the technical issues with NI coils is their thermal and electromagnetic behavior when a local normal transition occurs. Given that multiple stacked coils are used in MRI, the interaction between coils must also be investigated, because a local normal transition may affect the other NI coils through magnetic coupling. In fact, when a local normal transition occurs, there is a possibility that large electromagnetic forces are applied to the other coils, or quench may be induced in some of them. Even though overcurrent tests of stacked NI coils have been conducted, the results are not helpful in actual MRI operation. In this study, we investigate the effects of the occurrence of a local normal transition in multi-stacked NI coil systems under conditions similar to those of actual operation, with a constant transport current below the coil's I c . The occurrence of a local normal transition is simulated by applying current to a heater inserted in manufactured small NI double pancake coils. To evaluate the interaction between NI coils, the voltage and changes in the generated magnetic field are measured at each coil. We also show the current distribution in the coils, as obtained by the partial element equivalent circuit method. The obtained results allow us to evaluate the interaction of the NI coils and evaluate coil protection methods.

Feline hip joint anatomy in magnetic resonance images.

The aim of this study was to develop an anatomical model of the feline hip joint for low-field magnetic resonance imaging (LF-MRI) based on high-field magnetic resonance imaging (HF-MRI). The study was performed on six adult clinically healthy European shorthair cats, aged 1-3years, with body weight of 2.8-4.4kg. The animals were examined with the use of the Vet-MRI Grande Esaote LF (0.25T) scanner and high-field Siemens Magnetom TRIO (3T) MRI scanner. In the LF-MRI, most satisfactory results in T1-weighted images were obtained when TE was 26ms in all three planes and when TR was 350-950ms in the transverse plane, 950-1150ms in the sagittal plane and 520-750ms in the dorsal plane. In T2-weighted images, TE was 90ms in the transverse and dorsal plane and 120ms in the sagittal plane. The results were presented as images acquired with LF-MRI scanners in three planes. The slice thickness was 3mm for each plane. In LF-MRI, muscles in the hip joint region and round ligament were well visualized. Unlike in LF-MRI, the cross section of the femoral nerve was identified in HF-MRI scans. In examinations of the feline hip joint, the main limitations of LF-MRI were a lack of reliable contrast between articular cartilage and synovial fluid as well as longer scan time. Despite the above, LF-MRI images were characterized by good contrast between bones and the surrounding soft tissues.

The assessment of lenticulostriate arteries originating from middle cerebral artery using ultra high-field magnetic resonance time-of-flight angiography

Time-of-flight angiography (ToF) was presented for the first time by Suryan and used by Hinshaw et al. This protocol allows to visualize blood flow within the vessels in vivo without the contrast administration, which is possible due to the large magnitude of magnetization, received from the moving spins and small magnitude of magnetization received from the stationary spins. Fourteen participants (male:female = 7:7) were analyzed, who have never been diagnosed with any central nervous system disease as well as any cardiovascular, metabolic disease and have never had any trauma. Although, the gold standard of cerebral vessel analysis is still DSA, ultra high-field 3D ToF-MRA shows clearer picture of all LSAs and the branches of LSAs in comparison to poor in contrast DSA imaging. Ultra high-field time-of-flight MRA is a valuable method in visualizing small perforating arteries, which can be used in the future as a diagnostic tool for clinical practice. The diversity of LSAs morphometry is vast and may alter during aging, thus the clinical anatomy of those vessels should be further investigated in vivo.

RF shield parallel-plate waveguide for travelling-wave MRI experiments at 3 T

Ultra high field magnetic resonance imaging systems suffer from the standing wave problems produced by conventional radiofrequency coils. This causes inhomogeneous fields degrading the image quality. To overcome this problems, propagation of RF waves by antennas inside a waveguide is suggested. We assessed the feasibility of using the magnet RF shield with aluminium strips to form a parallel-plate waveguide for travelling-wave magnetic resonance imaging at 3 T. Imaging results showed that a number of constraints must be solved before good image quality can be obtained. A brief discussion is presented on the possible sources or error and interference. Despite these limitations, results are really encouraging to continue investigating the implementation of this approach.

RF Aspects of High-Field Magnetic Resonance Imaging (HF-MRI): Recent Advances

High-field magnetic resonance imaging (HF-MRI) brings superior imaging with high contrast and signal-to-noise ratio (SNR). For scanning systems higher than 3.0 T and Larmor frequencies above 128 MHz, wavelength and higher tissue conductivity can cause distortion of the electromagnetic fields, leading to degraded image quality. This paper will show current trends in HF-MRI to mitigate some of these issues and provide a linkage between traditional MRI components and novel structures for HF-MRI. Transmit and receive structures, as well as the use of metamaterials for improved excitation and SNR, will be covered. Other examples of these recent trends will be potential antenna structures to replace current coil-based technology, and then finally, receiver/patient protection circuits will be covered.

GantryMate: A Modular MR-Compatible Assistance System for MR-Guided Needle Interventions.

Percutaneous minimally invasive interventions are difficult to perform in closed-bore high-field magnetic resonance systems owing to the limited space between magnet and patient. To enable magnetic resonance–guided needle interventions, we combine a small, patient-mounted assistance system with a real-time instrument tracking sequence based on a phase-only cross-correlation algorithm for marker detection. The assistance system uses 2 movable plates to align an external passive marker with the anatomical target structure. The targeting accuracy is measured in phantom experiments, yielding a precision of 1.7 ± 1.0 mm for target depths up to 38 ± 13 mm. In in vivo experiments, the possibility to track and target static and moving structures is demonstrated.

Accuracy of nigrosome-1 detection to discriminate patients with Parkinson's disease and essential tremor.

The use of susceptibility weighted imaging in high field magnetic resonance imaging scanners can detect the nigrosome-1 area located in the caudo-lateral region of the pars compacta in the substantia nigra. This structure comprises a significant amount of dopaminergic neurons and degenerates in the early stages of Parkinson's disease. Essential tremor is a neurological condition that in some cases could be confused with the early stages of Parkinson's disease with a possible error in clinical diagnosis. Our purpose is to evaluate the accuracy of nigrosome-1 detection by high resolution magnetic resonance imaging to discriminate Parkinson's disease from essential tremor. A case-control study compared patients with a clinical diagnosis of Parkinson's disease and essential tremor. Magnetic resonance imaging studies were performed using a 3T magnetic resonance imaging scanner. The susceptibility weighted imaging sequence was obtained in the axial plane with an isotropic voxel of 0.75 mm. Two independent neuroradiologists evaluated the images without access to clinical patient data. Sixteen patients were included in each group (Parkinson's disease and essential tremor). Average age: Parkinson's disease group: 71.3 (SD 6.3) and essential tremor group: 68.3 (SD 12.3). For the first evaluator, the nigrosome-1 area was absent in 15 patients with Parkinson's disease and in two with essential tremor and for the second evaluator was absent in 15 patients with Parkinson's disease and four with essential tremor. The sensitivity/specificity for the diagnosis of Parkinson's disease was 93.75%/87.5% for the first evaluator and 93.75%/75% for the second evaluator. The detection of the nigrosome-1 area is a useful tool in the differential diagnosis between Parkinson's disease and essential tremor, with high sensitivity and specificity.

The Influence of Magnetic Fields (0.05 T ≤ B ≤ 7 T) on the Response of Personal Thermoluminescent Dosimeters to Ionizing Radiation

We investigated the main question of whether thermoluminescent dosimeters indicate the correct dose when exposed to magnetic fields from low stray fields up to high magnetic resonance imaging fields inside human magnetic resonance imaging scanners (0.05 T ≤ B ≤ 7 T) during and after irradiation. Medical personnel working in radiology, oncology, or nuclear medicine are regularly monitored with thermoluminescent dosimeters. They might also enter the magnetic field of a magnetic resonance imaging scanner while supervising patients as well as during positron emission tomography-magnetic resonance imaging and magnetic resonance imaging-linac integrated imaging systems and will therefore be exposed to the magnetic fields of magnetic resonance imaging scanners and low stray fields of several millitesla outside of the magnetic resonance imaging scanner, not only before and after, but also during irradiation. Panasonic thermoluminescent dosimetry badges and ring dosimeters for personal monitoring were exposed to magnetic fields originating from a 7 T and a 3 T magnetic resonance imaging scanner as well as neodymium permanent magnets. Four different sealed Cs sources were used in two sets of experiments: (1) magnetically induced fading: irradiated thermoluminescent dosimeters (D ≈ 100 mSv) were exposed to a strong magnetic field (B = 7 T) of a human high-field magnetic resonance imaging scanner after irradiation; no magnetically induced fading (magnetoluminescence) for LiBO:Cu or CaSO:Tm was observed; (2) magnetically induced attenuation: thermoluminescent dosimeters were placed during irradiation in a magnetic field for about 60 h; a significantly reduced dose response was observed for LiBO:Cu-interestingly not at maximum B ≈ 7 T but at B ≈ 0.2 T. This experimental observation is possibly relevant especially for medical and technical personnel in nuclear medicine before and during a magnetic resonance imaging scanning procedure. Follow-up studies need to be made to clarify the kinetics of this effect.